One
of the major challenges facing humankind is to provide an equitable
standard of living for present and future generations: adequate
food, water, energy, safe shelter and a healthy environment. But,
global environmental issues such as land degradation, loss of
biodiversity, stratospheric ozone depletion along with human-induced
climate change, threatens our ability to meet the basic human needs.
The Third Assessment Report (TAR) of the Intergovernmental Panel on
Climate Change (IPCC) reaffirms that the climate is changing in ways
that cannot be accounted for by natural variability and that ‘global
warming’ is happening. Global mean temperatures have risen (0.6oC
in the last century), with the last decade being the warmest on
record. Climate change will, in many parts of the world, adversely
affect socio-economic sectors, including water resources,
agriculture, forestry, fisheries and human settlements, ecological
systems and human health, especially in developing countries due to
their vulnerability.

Vulnerability to climate change is closely related to poverty, as
the poor have fewer financial and technical resources. They are
heavily dependent on climate-sensitive sectors such as agriculture
and forestry; they often live on marginal land and their economic
structures are fragile. This is true for a developing country like
India where agriculture remains the mainstay of the economy,
contributing nearly 27% of the total Gross Domestic Product (GDP)
and employing nearly two-thirds of the country’s population.
Agriculture exports account for 13 to 18% of total annual exports of
the country. However, given that 62% of the cropped area is still
dependent on rainfall, Indian agriculture continues to be
fundamentally dependent on the weather.

Climate change will have an economic impact on agriculture,
including changes in farm profitability, prices, supply, demand and
trade. The magnitude and geographical distribution of such
climate-induced changes may affect our ability to expand the food
production as required to feed the populace. Climate change could
thus have far reaching effects on the patterns of trade among
nations, development and food security.

Agriculture is sensitive to short-term changes in weather and to
seasonal, annual and long term variations in climate. Crop yield is
the culmination of a diversified range of factors. Parameters like
soil, seed, pest and diseases, fertilizers and agronomic practices
exert significant influence on crop yield. The burgeoning
population, along with human-induced climate change and
environmental problems is increasingly proving to be a limiting
factor for enhancing farm productivity and ensuring food security
for the rural poor.

Agricultural productivity can be affected by climate change in two
ways: first, directly, due to changes in temperature, precipitation
and/or CO2 levels
and second, indirectly, through changes in soil, distribution and
frequency of infestation by pests, insects, diseases or weeds. Acute
water shortage conditions, combined with thermal stress, could
adversely affect wheat and, more severely, rice productivity in
India even under the positive effects of elevated CO2 in
the future. The mean temperature in India is projected to increase
by 0.10 C
to 0.30C
in kharif (summer) and 0.30C
to 0.70C
in rabi (winter) by 2010 and to 0.40C
to 2.00C
in kharif and 1.10C
to 4.50C
in rabi by 2070 (IPCC, 1996). Mean rainfall is projected not
to change by 2010 but may increase by 10% during rabi by
2070. At the same time, there is an increased possibility of climate
extremes, such as the timing of onset of monsoon and intensities and
frequencies of droughts and floods. The findings of several studies
carried out in India are given in Table-1.

Crop

Scenario

Projection

Reference

Rice

20C rise

1.50C
rise + 2 mm rainfall rise + 460 ppm CO2

-0.06 - 0.075 ton /
hec

+12% in South India

Sinha & Swaminathan
(1991) Saseendran et al (1999)

Wheet

20C rise
+ 425 ppm CO2

-1.5 - 5.8% in sub
tropical India

-17-18% in tropical
India

-10% in Punjab,
Haryana

Aggarwal & Kalra
(1994)

Kumar & Parikh
(1998)

Maize

20C rise
+ 425 ppm CO2

-7-12% in North
India

Chatterjee (1998)

From
Table-1, it is clear that most of the staple food crops in India are
going to be adversely affected. For sugarcane, it was observed that
for every 1°C rise in temperature, there would be a marked reduction
in its yield (Chattopadhayay 2000).

Impact of climate change on soil

The
soil system responds to the short-term events such as episodic
infiltration of rainfall and also undergoes long-term changes such
as physical and chemical weathering due to climatic change. The
potential changes in the soil forming factors directly resulting
from global climate change would be in the organic matter supply,
temperature regimes, hydrology and changes in the potential
evapotranspiration. Both the organic matter and carbon to nitrogen
ratio(C: N ratio) will diminish in a warmer soil temperature regime.
Drier soil conditions will suppress both root growth and
decomposition of organic matter and will increase vulnerability to
erosion. Increased evaporation from the soil and accelerated
transpiration from the plants themselves will cause soil moisture
stress.

Impact on pests, diseases and weeds

Incidence of pest and diseases would be most severe in tropical
regions due to favourable climate/weather conditions, multiple
cropping and availability of alternate pests throughout the year.
Climate change is likely to cause a spread of tropical and
subtropical weed species into temperate areas and to increase the
numbers of many temperate weed species currently limited by the low
temperature at high latitudes.

The
above facts demand urgent measures, from the scientific community
and the government. Some of the adaptation measures at the farmers’
level could be:

q

For short-season crops such as wheat, rice, barley, oats, and
many vegetable crops, extension of the growing season may allow
more crops in a year.

q

Longer-season cultivars can be sown to provide a steadier yield
under more variable conditions.

q

Late
maturing varieties and alteration of time of sowing to take
advantage of the longer growing seasons needs to be adopted.

q

Changes in cropping pattern (shift from rice–wheat cropping
system to other favourable crop mix) may be adopted. Crop
diversification in Canada and in China has been identified as an
adaptive response.

Water resources in the semi-arid regions are expected to
decrease due to climate change. Increased evaporation (resulting
from higher temperature), combined with changes in precipitation
characteristics (amount, variability and frequency), has the
potential to affect agriculture - the predominant user of water.
Better water management is required for enhancing crop
productivity and ensuring food security. Generally, irrigated
agriculture is less adversely affected than dry land agriculture
but adding irrigation is a costly affair as it is dependent upon
the availability of water supplies.

q

Added nitrogen and other fertilizers would likely be necessary
to take full advantage of the CO2 effect
but may have deleterious effects on humans and aquatic
ecosystems.

Water and nutrient management thus, have to be redefined in various
agro-ecologies to meet the future demands.

Strategies for facing the challenge

Specific measures can only provide a successful adaptive response if
they are adopted in appropriate situations. A variety of issues need
to be considered, including land-use planning, watershed management,
disaster vulnerability assessment, consideration of port and rail
adequacy, trade policy, and the various programmes countries use to
encourage or control production, limit food prices, and manage
resource inputs to agriculture.

Important strategies for improving the ability of agriculture to
respond to diverse demands and pressures include:

q

Improved training and general education of populations dependent
on agriculture.

q

Research on new variety development, incorporating various
traits such as heat and drought tolerant, salt and pest
resistant should be given prime importance.

q

Food programmes and other social security programmes, to provide
insurance against local supply changes.

q

Infrastructure facilities like transportation, distribution and
market need to be improved.

q

Existing policies may limit efficient response to climate
change. Changes in policies such as crop subsidy schemes, land
tenure systems, water pricing and allocation, and international
trade barriers could increase the adaptive capability of
agriculture.

Conclusion

Signals of climatic change are already visible. Global climate
change is going to affect major crops like rice, wheat, maize in
India. Climate is the least manageable of all resources. Hence, to
avert the ill effects of climate change, more attention has to be
paid to other resources and technologies viz. soil, irrigation
water, nutrients, crops and their management practices, to sustain
the productivity and to ensure food and environmental security to
the country. Adaptive measures are to be taken in a timely fashion,
both at the farmers’ level (backed by strong agriculture/climate
research and application oriented outputs) as well as at the policy
makers’ level to enable the small and marginal farmers to cope with
the adversities of climate change. q

References

Aggarwal, P.K. and Kalra, N. (1994). Analyzing the limitations set
by climatic factors, genotype, and water and nitrogen availability
on productivity of wheat. II. Climatically potential yields and
optimal management strategies. Field Crops Res., 38, 93-103.

Chatterjee, A. (1998). Simulating the
impact of increase in Carbon Dioxide and temperature on growth and
yield of Maize and Sorghum. M.Sc. thesis, Division of Environmental
Sciences, Indian Agricultural Research Institute, New Delhi.

Chattopadhayay, R. (2000). Simulating the impact of
climatic variability and climate change on the productivity of
sugarcane. Ph.D. Thesis, Division of Environmental Sciences, Indian
Agricultural Research Institute, New Delhi.

IPCC (1996). Climate Change 1995: Impacts,
Adaptations and Mitigation of climate change: Scientific-Technical
Analysis. Report of the Working Group II of the Intergovernmental
Panel on Climate change, Cambridge University Press, London and New
York.